Electron discharge device



Nov. 14, 1950 H. L. STEELE, JR

ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 1 Filed Nov. 4, 1944 INVENTORIH. z, .SrEEAE, J76.

ATTORNEY Nov. 14, 1950 H. L. STEELE, JR

7 ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 2 Filed Nov. 4, 1944 INVENTORW 5 1 W H m V E N R Q T A Patented Nov. 14, 1950 ELECTRON DISCHARGEDEVICE Howard L. Steele, Jr., Bloomfield, N. J., assignor toWestinghouse Electric Corporation, East Pittsburgh, Pa., a corporationof Pennsylvania Application November 4, 1944, Serial No. 561,890

This invention relates to electron discharge devices of the characterknown as magnetrons, and more particularly to tuning means for the same.v

Considerable attention has been directed recently to the possibilitiesof tuning magnetrons that the output therefrom may be varied as to wavelength. Efforts to accomplish this desideratum have been largelyconfined to provision of movable members, usually in the resonantcavities, but the results have been unsatisfactory from the standpointof loss of power attendant upon introduction of obstacles in thecavities tending to interrupt or impede the magnetic flux therethrough.According to the present invention, means are provided for varying theinternal or tube capacity, and consequently the output frequency,without appreciable loss of power output. Thus, the objectives of tuningand maintaining high rating of output are advantageously solved.

More specifically, an object of the invention is to utilize strapping ofthe segments as the capacitative tuning means.

Another object of the invention is to require transmission of a minimumamount of motion from the exterior to the interior of the device fortuning purposes.

A further object of the invention is to require minimum alteration ofdimensions of presentday magnetrons to adapt the same to include theinvention.

Yet another object of the invention is to provide effective, simple andwide-range electrical tuning means for a magnetron.

Other objects of the invention will appear to those skilled in the artas the description progresses, both by direct recitation thereof and byinference from the context.

Referring to the accompanying drawings in which like numerals ofreference indicate similar parts throughout the several views;

Figure 1 is a vertical central sectional view of a magnetron constructedin accordance with and showing the preferred form of tuning means of thepresent invention;

Figure 2 is a cross-sectional view taken on line 11-11 of Fig. 1;

Figure 3 is a detail sectional view of a part the magnetron as on lineIII-III of Fig. 2;

Figure 4 is a perspective view of the straps or rings and indicatingangular relationship thereof when assembled in the magnetron;

Figure 5 is a detail cross-section of the engaging shoulders of theanode;

strap-- 11 Claims. (Cl. 250-27.5)

Figure 6 is a cross sectional view correspondin to Fig. 1 and showing amodified-construction of tuning means therein;

Figure 7 is a cross sectional view on line VII-VII of Fig. 6;

Figure 8 is a plan with cover or end plate removed of a magnetron havinga modified construction of tuning means therein;

Figure 9 is a vertical sectional view corresponding to Fig. 6 andshowing a further modified construction of tuning means.

Figure 10 is a sectional plan of yet another construction tuning means.1

Figure 11 is a perspective view of a strap sectio as utilized in theconstruction of Fig. 10; and

Figure-l2 is another perspective view of the strap section modified forelectrical tuning.

Referring now specifically to the embodiment of the inventionillustrated in the several figures, and with attention initially devotedto Figs. 1 to 5, the reference numeral I0 designates a cylindricalmetallic magnetron body, the ends whereof have cover or end plates Hsealed thereon that the interior may be evacuated. Within and as anintegral part of said body is the usual magnetron anode structure [2 ofgenerally cylindrical shape but shorter than the outer part of the bodyso as to provide end spaces [3 between the anode and said end plates H.The anode structure'is axially hollow to provide a cathode cavity for acathode l4 and radiating from this cathode cavity are a plurality ofresonant cavities [5, each having, in the form shown, a cylindricalportion parallel to the cathode cavity and each having a longitudinalconstriction or slot opening into the cathode cavity. A desiredcapacitance exists across the constricted space between the cavityfaces, and a concentration of E-lines will exist thereat in use. Thewalls between cavities are generally designated segments or vanes IS.The ends of the cathode cavity and the ends of said resonant cavities,including said constrictions, open into the end spaces l3. Cathode l4passes axially through the cathode cavity, adequately spaced from theanode, and is supported In the pre--' 3 ferred form of the presentinvention, however, the strapping of both series of alternate sectionsis accomplished at a single end of the anode. Accordingly, at one end ofthe anode body, and here shown at the upper end and at the edge of thesegments next the cathode cavity, there is provided an annular steppedrecess providing what may be termed a deep step i9 and a shallow step20. The deeper step is nearest the cathode and the shallow step is oflarger diameter than the deep step. A cylindrical riser wall 2| extendsfrom the rear of the deep step to the front edge of the shallow step,and a cylindrical riser wall 22 extends from the rear of the shallowstep to the end face of the anode body or segments thereof.

A strap in the form of a washer-like ring 23 is mounted on the deep stepbut in a manner to only contact the step in every alternate segment.

As the anode shown has eight segments, said ring 23 is provided withonly four evenly spaced cars 24 for engagement with four alternatesegments. Said ears project radially beyond the general peripheraloutline of the strap and bend downward next their outer ends, as at 25,so that the only contact of said strap with the anode will be thecontact of the said downwardly bent ear portions against the riser wall2| of the alternate sections. and against the rear of the lowerstep. Thestrap is preferably secured in place by soldering the contacting bentear portions to the riser wall. Similarly, an upper strap 23a isprovided for the shallow step, this strap also having ears 24a withdownwardly bent outer ends 250. Thereare likewise shown only four earson this strap 2-30. and they are located in'theassembly to seat on theshallow step of the segments intervening between the segments engaged bythe ears of the first-mentioned or lower strap 23. The alternatingrelationship of ears is indicated in Figure l. The ears of the upperstrap fit against the riser of the shallow step and are soldered inplace. Both straps are provided with large central openingsfor'appropriate clearance around the cathode. Attention is directed tothe fact'that each segment makes contact with no other part of thedevice than the particular alternating sections to which the" ears aresoldered, and the sections make no contact with each other, but ratherprovide a space, hereinafter referred to as the strap space, between thesaid straps.

The construction as thus far described provides", by virtue of theparallel straps and intervening strap space, a relatively high strapcapacitance which parallels the capacitance of the cavity constrictionsor slots. Electrons introduced into the slot space will change thecapacitance between the straps. This change of capacitance is the resultof the electrons changing the dielectric constant of the strap space andthe change. will depend in extent upon the number of electrons in saidstrap space; more electrons in the space result in decreased capacity.As a part of the length of the cathode passes through the straps; itserves as a direct source of electrons thereat: for entry into saidspace. Control of quantity of electrons from the cathode to said strapspace is obtained'by'interposing a grid 26.

It may be said at this point that utilization of the magnetron cathodeas a source of electrons both for power and for tuning is conducive tosimplicity and to effective and eificient operation, but itis within thescope of the invention to provide separate sources of electrons forthese purposes if so desired. Furthermore, it may be pointed out thatelectrons emitted from the oathode travel in approximate cycloidal pathsunder the influence of the magnetic field, and when the magnetron isoscillating, electrons will follow the cycloidal paths and traverse thestrap space, except as blocked or controlled by the grid.

Inasmuch as the grid 26 will be heated by radiation from the cathode andby bombardment of electrons, it is desirable to have the grid in theregion of lowest operating temperature and least emission. Thisdesideratum is agreeably satisfied by situating the grid next the end ofthe cathode, which also is the most desirable position for the straps;thus both conditions are satisfied. It is to be understood that nearnessof the rid to the cathode may be made to meet conditions of both heatand electron emission so as to positionthe grid at the most optimumspacing between cathode and strap.

As one convenient means for mounting grid 26, a cylindrical ceramic 21supporting both the cathode and grid may be provided. Said ceramic isshown as having successively smaller girth areas, the largest of whichis next the top,- and each successive smaller girth portion therebyprovides a downwardly facing shoulder. A metal ferrule 23 around thelargest girth portion has a flange under the first shoulder and anotherflange at its upper end welded to an end plate 29 in turn secured to thelead-in rod I 1. One of the smaller or intermediate girth portions ofthe ceramic 2? receives and sustains the upper end of grid 26, and thenext smaller or lower girth portion is shown receiving the end of thecathode thereon.

A lead-inconnection 30 is secured to the rid at the upper or securedpart of the grid, the connection passing to the exterior without contactwith the magnetron wall through a suitable fitting 3| which includesinsulation as usual. The grid has a length shown as locating the lowerend of the grid just below the lower strap. A potential may therefore beapplied to the grid and varied as desired to vary the gradient at thegrid-surrounded part of the cathode, thus controlling the number'ofelectrons that get into the strap space, and this introduces desiredregulation of the strapspace capacity whereby control of the potentialto the grid effects the desired tuning,

The construction of Figures 6 and 7 provides a magnetron body, anode,resonant cavities, end plates and end cavities as described in generalabove. although for simplifying disclosure, illustration of the cathodeis omitted in these figures since its presence, support and function arein accordance with prior art practice. As shown, concentric cylindricalstraps or rings 32 are mounted on the upper part of the anode body andwithin the end space. These straps are secured one to alternate segmentsifia of the anode body and the other to the intervening alternatesegments, said straps contacting only the alternate segments to whichattached and being spaced from each other leaving a strap spacetherebetween. This strap space is upwardly open, that is, opens towardthe end plate for the end space in which the straps are located. Saidstraps are preferably rigid and are soldered to the respective alternatesegments. The capacitance between said straps exerts its influence onthe internal or tube circuit and is therefore one of the factorsdetermining the frequency and wavelength of the magnetron output.

Means are provided for varying the capacitance between said cylindricalstraps. In the showing of Figures 6 and 7 the means mentioned 7comprises a cylindrical member such as sleeve 34, the wall thicknesswhereof is less than width of the strap space, and the diameter whereofis intermediate of the diameters of the two straps.

Consequently, by mounting the said cylindrical member coaxial to thestraps, it may be moved into and out of the strap space in an axialdirection. Said cylindrical member or sleeve 34 may be either adielectric or a conductor, and as shown, is a dielectric. Use of adielectric sleeve tends to lower the output frequency, whereas use of ametallic sleeve would tend to raise the frequency. By having like strapsat both ends of the anode body, with a movable member or.

sleeve for each strap space, tuning effect can be applied at both, andsaid sleeves may then be both metallic, both dielectric or one metallicand the other dielectric.

Movement of the sleeve is effected by means of a screw shown fast upon aplate 36 with the rim of said plate annularly channeled to receive andhold the said sleeve. At the outside face of said plate is secured witha vacuum tight joint the lower end of a bellows 31, the upper end ofwhich is sealed to the end plate. Depending into the bellows androtatable in the end plate Ila is a nut 38 rotation of which moves thescrew longitudinally. The nut 38 is made integral at its outer end witha dial or disc 39' shown of the same diameter as the magnetron body soas to be readily accessible in use for ported by alternate segmentsandthe other ring: connected to and supported by the intervening"alternate segments. In a sequential series within the strap space may besituated a plurality of short, parallel and electron emissive filamentsor auxiliary cathodes 40. By heating these au'xiliary cathodes,electrons emitted will decrease the capacitance and tend to increase thefrequency, since by well known formula,

21rvLC' where Linductance and C'capacity, it is possible by heating thecathode more or less to obtain desired adjustment of electron emissionof the auxiliary cathodes and desired tuning.

Preferably, however, the emission of auxiliary cathodes 40 is gridcontrolled. For that purpose I show a grid 4| surrounding each auxiliarycathode. By appropriate application of voltage bias on the grids 4|, thenumber of electrons in the strap space may be varied and controlled.

The foregoing embodiments of the invention have structures relying uponcapacitance between straps, but modification may be incorporated thereinfor utilizing capacity to ground. Exemplary of such modification, Figure9 utilizes a single cylindrical strap 32b for alternate segments lfib,strapping of the other or intervening segments being effected bycorresponding arrangement at the opposite end (not shown) of the anodebody. A metallic sleeve 342) having plate 3% integral therewith ismovable coaxially within said strap but out of contact therewith.

frequency Said plate and sleeve are operated by screwu35,

nut 38 g and dial 39 as previously described in connection with Figs. 6and '7 and vacuum sealing is obtained by a bellows 31.

Other strappingconstructions than full cylin- V For instance, a

ders can be made tunable. prevalent form of strapping comprises arcuateechelon wires each of which connects alternate 1 segments, withsuccessive wires in overlapping relation and with successive wiresconnecting different pairs of segments and constituting two series ofstraps. In order to introduce high capacitance in strapping of thischaracter, I uti' lize instead of wires, as shown in Figures 10, 11 and12, arcuate plates or sleeve sections 42 with feet 43 next their ends.Each anode segment I60 j has two holes 44, 45 in its end face, one hole44 being closer to the axis than the other hole45.

The sleeve sections have one foot in the inner hole 44 of one segmentand the other foot in the Interouter hole 45 of an alternate section.vening segments are-correspondingly strapped, thereby providing twoseries of overlapping straps for the alternate segments. Dielectricstrap sections 46 are movable into and out of the strap spaces betweensections in a rotative direction.

By greater insertion of the dielectric strap sections into the strapspace, the capacitance is correspondingly increased. All of said strapsections 46 may be mounted from a ring 41 in the end space, said ringbeing oscillated by a lever 48 having appropriate exterior protrusionand vacuum sealing.

sulators is carried a filament or cathode 5|, which produces electronsroughly in, proportion to its temperature and which thereby changes thestrap space capacitance and effects tuning. As

explained before, decrease of capacitance 'resulting from presence ofthe electrons in the strap space obtains increased frequency.

I claim:

1. A magnetron comprising an anode body,

having end spaces at the ends thereof and having a cathode cavity andcavity resonators extending 1 I from one end space to the other andhaving a cathode in said cathode cavity, said anode body providingsegments between successive. cavity resonators, strap means connectingalternate segunents, said strap means providing an adjacent "strap.space, and electronic means operative in 1 said strap space for changingthe capacitance in said strap space.

2. A magnetron comprising an anode body having end spaces at the endsthereof and having a cathode cavity with a cathode therein and havingcavity resonators extending from one end space to the other and havingsegments between successive cavity resonators, straps at one end spaceeach strap being connected to alternate segments, and electroniccapacity-changing means adjacent to said straps and effectivetherebetween to change capacity between said straps.

3. A magnetron comprising an anode body having end spaces at the endsthereof and having a cathode cavity with a cathode therein and havingcavity resonators extending from one end space to the other and havingsegments between successive cavity resonators, straps at one end spaceeach strap being connected to alternate segments, and rid controlledelectronic capacitychanging': means adjacent to said straps andeffective. therebetween for changing the. capacity between said straps,

4. A magnetron comprising an anode body having end. spaces at the endsthereof and having a cathode cavity and cavity resonators radiating fromthe cathode cavity and extending from one endspace to the other andhaving a cathode in said cathode cavity, said anode body providingsegments between successive cavity resonators, straps at one end spaceproviding strap space between said straps and said strap space having anopening at its edge communicating with said endv space, a' gridoppositesaid opening, and means in proximity to said opening for supplyingelectrons to said strap space under control of said grid.

5. Amagnetron comprising an anode body having end spaces at the endsthereof and having an axial cavity and cavity resonators radiating fromthe axial cavity and extending from one end space to the other, saidanode body providing segments between successive cavity resonators,straps perpendicular to the axial cavity next to one endv space and onestrap joining alternate segments and the other joining the interveningsegments, said straps being annular and thereby providing centralopenings, a grid in said openings, and a, cathode in said axial cavityand in part within said grid.

6. A magnetron comprising an anode body having an axial cavity andcavity resonators radiating from the axial cavity, said anode bodyproviding segments between successive cavity resonators, strapsextending beyond said axial cavity and each joined to different segmentsfrom the other, and cathodes disposed between said straps. for changingthe capacity therebetween.

7. A magnetron comprising an anode body having an axial cavity andcavity resonators radiating from the axial cavity, said anode bodyproviding segments between successive cavity resonators, coaxial strapsextending beyond said axial cavity and each joined to different segmentsfrom the other, and cathodes disposed be- 8 and grids around saidcathodes for controlling electron flow and change of capacity.

9. A magnetron comprising an anode body having an axial cavity andcavity resonators-radiating from the axial cavity, said anode bodyproviding segments between successive cavity resonators, arcuate platesections, one from each segment to an alternate segment therebeyond, anddielectric means adjustably insertable between successive said sectionsfor capacity control therebetween.

10. A magnetron comprising an anodebody having an axial cavity andcavity resonators radiating from the axial cavity, said anode body 7providing segments between successive cavity resonators, a cylindricalstrap projecting from said segments coaxial with said axial cavity, anda capacity-changing sleeve insertable in said cylindrical strap, saidsleeve having. a bottom wall there-across also insertable in saidcylindrical strap.

11. An electron-discharge device comprising: a cathode; an anodestructure, spaced from said cathode, and incorporating a cavityresonator; a pair of spaced conducting members electrically connected topoints of opposite polarity on said cavity resonator; an electron-sourcedisposed intermediate said conducting members for creating a spacecharge therebetween; and means adjacent said electron-source and saidconducting members for establishing a magnetic field transversely of thepath between said electron-source.

and said conducting members.

HOWARD L. STEELE, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,115,521 Fritz et' al. Apr. 26,1938 2,144,222 Hollmann Jan. 17, 1939 2,154,758 Dollenbach Apr. 18, 19392,241,976 Blewett et al. May 13, 1941 2,243,829 Brett et a1 June 3, 19412,408,235 Spencer Sept. 24, 1946 2,408,903 Biggs Oct. 8, 1946 2,409,913Tonks Oct. 22, 1946 2,414,084 Bowen Jan. 14, 1947 2,414,085 Hartman Jan.14, 1947 2,422,465 Bondley' June 17, 1947 FOREIGN PATENTS Number CountryDate Great Britain Apr. 2, 1936

